Although gallstones account for a considerable amount of patient morbidity and mortality, relatively little research using modern sophisticated techniques has been done concerning their formation, growth or prevention. Recently, physical chemists have demonstrated that cholesterol, a component in over 80 percent of human gallstones, is kept in solution by its incorporation along with bile salts and phospholipids into small molecular complexes (micelles). The concentrations of these three constituents in bile are critical to proper micelle formation. Many processes are involved in the development of a cholesterol gallstone but current research suggests that production of an abnormal bile supersaturated with cholesterol is the first and critical step necessary for cholesterol gallstone formation. The role of the gallbladder has not been adequately studied. The objective of this research will be the study of factors which can alter bile in such a way as to cause cholesterol precipitation and gallstone formation.